Danny, I did several projects around my place with my <font color=red> Farmal 340</font color=red>. Using a scoop to dig a ditch is similar to using a box blade. When digging a ditch controlling depth with the three pt. requires keeping a close watch on height of the three pt. Don't go fast until you get the hang of controlling depth of the cut. Make a shallow cut to remove sod first.
Mark is right about having a <font color=blue> Hydraulic Top Link </font color=blue>. I had one on the <font color=red> Farmal </font color=red>. It is very useful to control angle of the cutting edge. When the scoop is full it will allow it to tip scoop back to keep dirt in. When emptying, scoop can be tilted forward. Which will allow the scoop to tilt back past center and completely empty.
If you are only digging the width of the scoop, the brackets that hold the scoop to your three pt will limit the depth. If ditch will be wider than your scoop, then depth would be limited by how far ditch is angled out from the center. If you want to dig a straight-sided ditch, making it wider than the scoop may be a problem because the tire on the side of the first cut will fall into the ditch. Then your tractor will be tilted. When the first cut is complete this may be the time to put a back blade or box blade on.
When digging a ditch I would mount the scoop toward the front of tractor. When I was moving dirt I mounted it toward the rear. That way you don't have to drive over the dirt you are moving.
Did I mention that a scoop does not hold very much dirt or sod./w3tcompact/icons/frown.gif I'm spoiled since I got a FEL./w3tcompact/icons/smile.gif
I back filled all around my pole barn with dirt. Also used it to haul all the sand into the barn before I poured the concrete. I dug several ditches for drainage around barn. They were only about 10" deep.
Hope these suggestions help you.
A little off subject. I still have a drag scoop that I used to dig dirt out of my basement 20 years ago /w3tcompact/icons/frown.gif. I don't use it any more. I can't find anybody to hold the handles while I run the tractor./w3tcompact/icons/laugh.gif